The present invention relates to optically active alkyl 3-aryl-3-hydroxypropionates represented by the general formula: ##STR2## wherein R.sup.1, R.sup.2, R.sup.3,R.sup.4 and R.sup.5 are hydrogen, hydroxyl, alkoxy of 1-4 carbon atoms, benzyloxy, fluorine, chlorine or bromine and R.sup.6 is alkyl, and a method for producing the above compounds.
Optically active alkyl 3-aryl-3-hydroxypropionates represented by the above formula (II) are new compounds which are synthesized by the inventors of the present invention.
The new compounds are useful as starting materials for asymmetric synthesis of biologically and pharmacologically active materials.
It is known that in the optically active alkyl 3-aryl-3-hydroxypropionates, ethyl 3-phenyl-3-hydroxypropionate and ethyl 3-(4-methoxyphenyl)-3-hydroxypropionate are obtained by a method of Mukaiyama et al. (Chem. Lett., 813(1985)) in which ketoester is asymmetrically reduced by using diamine, a method of Soul et al. (J. Am. Chem. Soc., 86, 725(1964)) in which a compound is resolved by kinetics with hydrolytic enzyme, and a method of Santaniero et al. (J. Chem. Soc., Perkin Trans. 1, 1987, 2753) in which asymmetric reduction using baker's yeast is mentioned. However, the compounds obtained by these methods have low purity, and the methods are not desirable industrially and effectively.
In other words, in the method of Mukaiyama et al., namely in the asymmetrical reduction of ketoester with diamine, the compound obtained has low purity (44%ee). The reduction is rather impractical because of the reaction conditions at a low temperature, e.g. -100.degree. C.
The advantage of hydrolysis using enzyme is that (-)-and (+)-enantiomers are obtained. However, in the mass production, there are difficult problems such as selection of a reaction solvent, immobilization of enzyme, and purification of the product. The product do not have enough optical purity (about 70%ee).
Moreover, the asymmetric reduction using Baker's yeast is troublesome and the product has low purity (about 60%ee).
For the above reasons, it is desired to develop a technique for obtaining both enantiomers of optically active alkyl 3-aryl-3-hydroxypropionates useful for common asymmetric synthesis.